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Turbo Boost and Hyper-Threading

Turbo Boost and Hyper-Threading technologies were introduced in the very first Bloomfield processors. They have passed the test of time and proved their effectiveness. Hyper-Threading helps make the system faster under multithreaded load whereas Turbo Boost improves performance when only some of the CPU cores are loaded. Both technologies have been transferred to the new six-core Gulftown.

Hyper-Threading adds six more virtual cores to the six physical cores of the Core i7-980X, so the operating system sees as many as 12 cores as the result.

This screenshot raises the question of are there any applications capable of using up all these resources? Besides, the cores share a single memory bus, and the latter may prove to be a bottleneck, unable to deliver data quickly to all the cores. I carried out a small test to check this out. I measured the frame rate of a popular 3D shooter while running some resource-consuming applications in the background. To be specific, I benchmarked the system in Far Cry 2, running a few copies of the WinRAR-integrated benchmark (which itself supports multithreading). The computer’s memory worked as DDR3-1600. I also performed this test on platforms with top-end Bloomfield and Lynnfield processors for the sake of comparison.

The Gulftown copes better than its four-core cousins with the multithreaded load. Its performance lowers less than that of its opponents when the background load increases, so the 3-channel memory subsystem seems to be sufficient for multithreaded environments.

The Turbo Boost implementation in the Core i7-980X is somewhat disappointing. After Lynnfield processors for the LGA1156 platform acquired the ability to increase the clock rate by 667 MHz above the default one, I expected to see something like that in the Gulftown as well, but Intel decided differently. The new six-core CPU is as conservative as the Bloomfield series in terms of Turbo Boost. Its frequency can be increased by means of that technology from the default 3.33 GHz by 266 MHz only – to 3.6 GHz. The table shows the Turbo Boost frequencies of the senior models of Gulftown, Bloomfield and Lynnfield processors.

Thus, the highest frequency of all top-end CPUs with the Nehalem microarchitecture is the same 3.6 GHz. Officially, the Core i7-980X can maintain that frequency even for two CPU cores, but I could only observe it working at 3.6 GHz when executing a single thread. When a second core was under load, the clock rate lowered to 3.46 GHz.

However, it must be noted that the CPU overclocking based on Turbo Boost depends not only on the activity of the cores but also on the power consumption of the CPU. Perhaps, the inability of the Core i7-980X to work at 3.6 GHz under dual-threaded load is due to its power consumption going beyond the prescribed limits.

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